PSet_06

PSet_06 - near its maximum value. Use a high enough...

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Spring 2003 10.450 Process Dynamics, Operations, and Control Problem Sets - 6 We’re interested in good control, so we’ll practice tuning with your process simulator. 1. First we must review the Bode plots. Choose a disturbance gain of 0.5 and time constant of 5 for a first-order process. Calculate the frequency response from the analytical formula. Prepare the Bode plots over a reasonable domain of frequency. Then run sim450 with a sine input. Extract the frequency response by comparing the input and output traces after the initial transients have died away. Do this for a sufficient number of frequencies to be a good test of the simulator. Plot the results on the analytical solution you have prepared. Note: What’s a ‘reasonable domain of frequency’? Make it illustrate a practical range of the frequency response. For example, use a low enough frequency that the amplitude ratio is
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Unformatted text preview: near its maximum value. Use a high enough frequency that AR has fallen to 5% or so. Higher frequencies, and thus even lower AR, make no useful difference in a practical chemical process. If you exit sim450, you will have access to the arrays contvar and distvar at the command line. You must compare these two traces to get the required amplitude ratio and phase angle. (It might be prudent to review the definition of radian frequency in Lesson 3.) 2. Follow Marlin Eq (11.6) to install integral and derivative modes in your controller. You will need to introduce a variable to store the accumulated error for the integral mode. 3. Use Ciancone and ZN recommendations to tune your controller for your first-order process. Install those constants and try it out on a step input. 1...
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